What is the recommended protocol for switching an adult male from xyosted (oxymetholone) to testosterone cypionate?

Switching from Xyosted to Testosterone Cypionate

Discontinue Xyosted and start testosterone cypionate 100 mg intramuscularly weekly on the same day, with no washout period required; measure serum testosterone at 3–6 months to confirm mid-normal levels (400–700 ng/dL) and adjust the dose accordingly. 1, 2

Understanding the Medications

Xyosted is subcutaneous testosterone enanthate, not oxymetholone (the expanded question contains an error—oxymetholone is an oral anabolic steroid unrelated to Xyosted). 3 Xyosted delivers testosterone enanthate 50–100 mg subcutaneously once weekly via autoinjector, whereas testosterone cypionate is administered intramuscularly. 3 Both are long-acting testosterone esters with similar pharmacokinetics, providing therapeutic levels for 1–2 weeks after injection. 1, 4

Transition Protocol

Timing of the Switch

• Stop Xyosted and administer the first dose of testosterone cypionate 100 mg intramuscularly on the same day; no washout is necessary because both formulations have overlapping durations of action. 1, 5
• If the patient prefers to avoid any potential overlap, you may initiate testosterone cypionate on the day the next Xyosted dose would have been due (7 days after the last Xyosted injection). 1, 5

Initial Dosing of Testosterone Cypionate

• Begin with 100 mg (0.5 mL of 200 mg/mL solution) intramuscularly once weekly; this regimen provides stable serum testosterone and is the standard initial therapy recommended by the Endocrine Society. 6, 1
• Preferred self-injection site is the vastus lateralis (thigh); the gluteal muscle may be used when another person administers the injection. 1
• Weekly dosing of 75–100 mg produces more stable serum testosterone concentrations than the traditional 200 mg every 2 weeks, which generates supraphysiologic peaks and subtherapeutic troughs. 6, 1

Monitoring After the Transition

First Testosterone Check

• Measure serum testosterone 3–6 months after switching to confirm achievement of the target mid-normal range of 400–700 ng/dL. 6, 1, 2
• For weekly injections, obtain the sample mid-interval (approximately day 3–4 after the dose) to reflect average exposure rather than a trough level. 1, 2
• Adjust the dose if the level is >700 ng/dL or <350 ng/dL; increase by 25 mg weekly if below target, decrease by 25 mg if above target. 6, 1, 2

Concurrent Safety Monitoring

• Check hematocrit at the 3–6 month visit because testosterone-induced polycythemia is dose-dependent and may appear early in treatment. 6, 1, 2
• Discontinue therapy immediately if hematocrit exceeds 54%; evaluate for hypoxia or sleep apnea and consider restarting at a reduced dose once hematocrit normalizes. 6, 1, 2
• For men ≥40 years, obtain PSA and digital rectal exam at baseline (if not done recently), repeat at 3–6 months, then annually; refer to urology if PSA rises >1.4 ng/mL within 12 months, PSA velocity >0.4 ng/mL per year, or the exam is abnormal. 6, 1, 2

Long-Term Monitoring

• Once therapeutic levels are stable, repeat testosterone testing every 6–12 months, then annually. 1, 2
• Continue annual hematocrit and PSA monitoring even when testosterone levels are stable. 1, 2

Rationale for Weekly Intramuscular Dosing

• Weekly 100 mg cypionate is superior to biweekly 200 mg for maintaining testosterone within the normal range, as biweekly dosing produces wide peaks (days 2–7) and troughs (days 13–14) that cause symptom fluctuation. 1, 7, 8
• Intramuscular testosterone cypionate costs approximately $156 annually versus $2,135 for transdermal preparations, making it the most cost-effective formulation. 1
• Some evidence suggests subcutaneous testosterone enanthate (Xyosted) may produce lower post-therapy estradiol and hematocrit compared to intramuscular testosterone cypionate, potentially due to more stable pharmacokinetics. 7 However, both formulations effectively restore testosterone to therapeutic levels. 7

Common Pitfalls to Avoid

• Do not draw testosterone levels immediately before the next weekly injection; this captures a trough rather than average exposure. Instead, draw mid-interval (day 3–4). 1, 2
• Do not wait longer than 6 months for the first post-transition testosterone check; early measurement at 3–6 months is essential to guide dose titration and detect adverse effects. 6, 1, 2
• Do not continue therapy if hematocrit exceeds 54%; this is a hard stop requiring immediate discontinuation regardless of symptom improvement. 6, 1, 2

Contraindications to Testosterone Therapy

• Active prostate cancer or breast cancer constitute absolute contraindications. 6, 1
• Baseline hematocrit >50% precludes initiation of therapy. 6, 1
• Untreated severe obstructive sleep apnea is an absolute contraindication. 6, 1